Question

Explain the gene therapy, with reference to treatment of SCID.

Answer 1

Gene therapy technique is based on recombinant DNA technology. Gene therapy is a new technique for the treatment of the disease at the genetic level.

Complete answer:
Gene therapy or gene transfer therapy is an experimental technique that uses genes to treat a disease. It involves the replacement of defective or faulty genes with healthy ones in order to treat genetic disorders. Gene therapy is an artificial method that introduces DNA into the cells of the human body. First gene therapy was successfully done in the year 1989.

There are two types of gene therapy depending upon the type of cells involved:
-Somatic Gene Therapy- It usually occurs in the somatic cells (vegetative cells) of the body. In this therapy, therapeutic genes or desired genes are transferred into the somatic cells or the stem cells of the body.
-Germline Gene Therapy- It usually occurs in the germline cells (sex cells) of the body. This process involves transferring healthy DNA into the cells responsible for producing reproductive cells i.e. eggs, or sperms. This method is adopted to treat the genetic disorder causing variations of genes which are passed on from parents to their offsprings. There are certain challenges in this method as a new gene is inserted into the body, the immune system of our body can reject the gene due to the action of our body cells on the foreign target.

Gene therapy in case of SCID (i.e. Severe Combined Immunodeficiency):
In SCID, a gene known as ADA gene that codes for the enzyme adenosine deaminase is mutated. For the repair of this effect, a retrovirus containing a functional wild-type ADA gene is injected into the parent's bone marrow ex-vivo and then again incorporated into the parent’s bone marrow. Inserted gene either integrates into the chromosome of the host at different sites away from the mutated gene or replaces the defective gene and produces functional enzymes.

Note: Gene therapy is a treatment for a number of diseases such as cancers, certain viral infections, or some inherited disorders. This technique is a targeted therapy and can be used on individuals as well as embryos.